Today, this version of the iPhone is really simply the equivalent of an iPod Touch, and should normally be purchased as such. That said, these are actually really great deals for people who just want an inexpensive MP3 player. It's important to be aware of the maximum iOS and system requirements any particular iPhone will operate with before purchasing.

iPhone 3GS specifications:

Maximum OS: iOS 6.1.6

iTunes Version iTunes: 8.2 or later

System Requirements: Mac OS X v10.4.11 or later or Windows Vista; or Windows XP Home or Professional with Service Pack 3 or later

Weight: 4.8 ounces

Display Resolution: 320 by 480 pixels (163 ppi)

Processor Speed: 600 MHz

Built-in RAM: 256 MB

Camera: 3.0 megapixels with video recording

Connection: 30-pin dock connector

We guarantee that our iPhones are genuine Apple iPhones and are available for phone contract to the carrier listed in the product name. This is important, because with services like "Find My iPhone" and other carrier theft prevention schemes, buying a phone from someone you don't know and may not be able to return can be a real problem. We also offer a 90-day warranty for the basic operation of the phone.

What is CDMA vs. GSM?

There are two basic technologies inside mobile phones: CDMA and GSM. In the United States, GSM is used by AT&T and T-Mobile. CDMA is used by Sprint, U.S. Cellular, and Verizon. Most of the rest of the world uses GSM, which is part of the reason why AT&T phones have been more popular overall: they can essentially be used worldwide just by popping out the sim and putting another one in.

In general, once a phone is registered as a Sprint phone, it's best just to keep that phone with that carrier due to Sprint's strict unlocking policies. The iPhone 5s, 5c, 6, and up can all be used on AT&T, T-Mobile, and Verizon. On iPhone 5 and earlier (and any Sprint phone), you should buy a phone that has the same the carrier listed that you plan on using.

Keep in mind that when you buy a used iPhone, you'll still need to communicate with your carrier to get the phone activated on their network. Note that iPhones are shipped from PowerMax without any SIM card. AT&T SIMs can be purchased from us at the same time as your phone; for other phones, you will need to get a SIM from them and activate it accordingly, and may necessitate a visit to one of their outlets.

We guarantee that our iPhones are genuine Apple iPhones and are available for phone contract. This is important, because with services like "Find My iPhone" and other carrier theft prevention schemes, buying a phone from someone you don't know and may not be able to return can be a real problem. We also offer a 90-day warranty covering the basic operation of the phone.